The invention is based on a liquid filter with a built-in pressure regulator for fuels.
A liquid filter of this kind, with a built-in pressure regulator for fuels, is known from U.S. Pat. No. 5,078,167, in which the otherwise separate components, such as the filter and pressure regulator, are combined in a common unit, of the kind known as returnless fuel systems (RLFSs). In this liquid filter, the pressure regulator functions with a diaphragm, which is acted upon by the pressure to be regulated at the outflow connector, counter to the force of a spring. A disadvantage of this liquid filter is that here the flow through the filter is from the inside outward, which can greatly reduce its service life, since dirt deposits can form bridges that reduce the inlet cross sections. This is especially critical when there are large amounts of dirt. Also, the pressure must be returned to one side of the diaphragm from the clean side of the filter, thus necessitating the formation of a chamber at the diaphragm, which is complicated. Another unfavorable aspect is that the pressure regulator is connected between the inflow connector and the tank connector, and accordingly is located entirely on the dirty side of the filter element. As a result, dirt particles can get into the valve of the pressure regulator and impair its function. In this pressure regulator, the valve itself is a component that is separate from the diaphragm, and thus this liquid filter with its pressure regulator is relatively complicated and expensive in design and requires many shaped sheet-metal parts. Moreover, this filter is designed to be installed in a tank and is poorly suited to be connected by means of lines.
A liquid filter with a built-in pressure regulator is also known from U.S. Pat. No. 4,011,848, in which the liquid filter is embodied essentially as a line-type filter, with the inflow connector and outflow connector disposed on the opposed face ends of the housing. A third connector leads radially and laterally away from the housing to the tank, in which a simple ball valve is provided as the pressure regulating valve. An additional safety valve is also associated with the outflow connector and is intended to block the connection to the tank if the fuel supply fails. Once again, in this liquid filter the pressure regulator is connected directly to the dirty side. The pressure regulator here functions without a diaphragm, and because of the ball valve used it is relatively imprecise and is vulnerable to soiling. From the standpoint of being built in, the fact that the connectors for the outflow connector and the tank connector are at right angles to one another is highly unfavorable in many applications. Furthermore, German patent document DE 42 42 242 A1 discloses a device for supplying the internal combustion engine of a motor vehicle with a fuel from a supply tank, in which several components are assembled to an aggregate. A filter element through which fuel flows axially or radially is arranged in a joint housing. It is; ring-shaped and arranged concentrically to the longitudinal axis of a fuel pump. The clean side of the filter element is connected directly with the suction connection of the fuel pump. A tubular connection branches from an outwardly expanding pressure connector of the fuel pump, and a spring loaded membrane pressure regulator which is arranged externally on the aggregate housing is connected with the tubular connection. The discharge side of the pressure regulator is unloaded to the dirty side of the filter element An integration of the pressure regulator in the filter is not provided in this aggregate.